1. Field
The present invention relates to a packet network system, more particularly relates to a packet network system achieving an improvement of the restoration ability from a suspension of communication services due to a node failure of communications devices (nodes) configuring a communications network and disasters etc. of a station buildings containing the nodes and improving flexibility of a network design and to a node of the same.
2. Description of the Related Art
In recent years, due to the increase of traffic over the Internet using the Ethernet® or IP (Internet protocol) packets, the rapid increase of ADSL (asymmetric digital subscriber line) users, and further the rise of VoIP (voice over IP) technology, in place of the conventional ring networks configured by SONET/SDH (synchronous optical network/synchronous digital hierarchy) apparatuses, attention has begun to be paid to networks of packet rings designed to directly process packets on a ring network and secure a packet band management and statistical multiplexing effect, that is, packet ring networks (hereinafter also simply referred to as “rings”).
In particular, in networks in city areas, the attention being paid to packet ring networks has become extremely high. For this reason, in the IEEE as well, standardization is proceeding in the IEEE802.17. Such recent packet rings are generally referred to as RPRs (packet rings) for distinguishing them from conventional token rings and FDDI (fiber distributed data interface) rings. Incidentally, RPRs use SRPs (spatial reuse protocols) already released by Cisco Co. Ltd. and have following features 1) to 5):
1) Support for bidirectional duplex ring networks;
2) Support for MAC (media access control) layers (layer 2);
3) High rate of effective use of used band;
4) Easy plug & play; and
5) Short switching time to a normal ring of within 50 ms at the time of failure.
As a packet ring network, below an explanation will be given of a RPR as a principal preferred example.
Note that, as known technologies related to the present invention, there are Japanese Patent Publication (A) No. 2006-129071 and IEEE802.17 draft V3.3. Japanese Patent Publication (A) No. 2006-129071 discloses communication by adding an apparatus recognition ID into an ATD frame of an RPR packet and identifying a node from a number of hops and a topology table. On the other hand, IEEE802.17 draft V3.3 is the standard of RPR.
FIG. 21 is a diagram showing a conventional RPR network. An RPR network 10 shown in the figure is a network with nodes #a to #f connected in a ring by an inside communication route 11i and an outside communication route 11o. Namely, the RPR network 10 employs a duplex ring configuration. Even if a failure occurs in one of the inside communication route 11i and outside communication route 11o, it is possible to continue communication by retransmitting the packet data by the other communication route.
The nodes #a to #f mainly function to send packet data. Each is configured by a transmission device, bridge node, router, server, RPR dedicated device, etc.
FIG. 22 is a diagram showing an example of the configuration of a network system using a conventional RPR network. This network 10 is a network configured by a network provider. User networks 51 and 52 are networks of end users. These user networks 51 and 52 are connected to each other via nodes #b and #e of the network 10.
A packet from the user network 51 is transmitted encapsulated into an RPR packet including an RPR header at the node #b. When the node #e receives this, the RPR header is removed and the remainder is transferred to the user network 52. Note that in such mode of utilization, a packet from the user network 51 is transferred to the node #e, while a packet from the user network 52 is transferred to the node #b. This is set for the nodes #b and #e in advance based on contracts between the users and the network providers (IEEE802.17 draft V3.3).
FIG. 23 is a diagram showing an example of the configuration of a network system comprised of two user networks connected to two different RPR networks. A packet from the user network 51 is transferred to the node #e by the RPR network 10, passes through a relay network 30, then is relayed to a node #i of an RPR network 201, transferred via a communication route 21i (or 21o) to a node #1, then arrives at the destination user network 52. Here, a packet transferred over the network 30 between the RPR network 10 and the RPR network 20 is an ordinary packet not having an RPR header. In this case, if assuming that the node #e or #i fails, the relay network 30 is disconnected, therefore the communications service between the user networks 51 and 52 is suspended.
Therefore, redundancy (node redundancy) of the nodes #e and #i of FIG. 23 and a redundancy network for connecting the redundant nodes become necessary. This is shown in FIG. 24. The figure is a diagram showing an example of the configuration of a network system using an inter-RPR network connection including node redundancy. The redundancy network is indicated by reference numeral 10.
However, the functions concerning such node redundancy is not prescribed in the standard RPR (IEEE802.17 draft V3.3). This is the problem.